Hiding/viewing of read messages

How can I hide read messages to view only unread in my inbox or any other folder in IMAP ?

You can read messages directly in the Unread folder - can you see it?

I do have an unread folder, but it shows ALL unread messages.  I would like to be able to configure my Inbox to show either both read and unread or only unread.  The reason is that I have a lot of folders for different categories of emails, and sometimes I may want to look at one folder only without seeing all of the already read mail.  Is this possible?

It is not possible to setup your inbox to display only your read or only your unread email, Inbox is a standard mailbox that receives new incoming email, it can not filter out read or unread messages without you moving the items to selected folder. You can however setup a search/smart folder for your read/unread or categorized email.